1. Field of the Invention
The present invention relates to intubation devices and, more particularly, to a device and method for inserting and confirming the placement of an endotracheal tube (ETT) in the trachea of a patient.
2. Description of the Prior Art
Certain types of illnesses and clinical conditions and injury can cause a patient's airway to become blocked or otherwise impaired, preventing adequate oxygenation and ventilation of the patient. When this occurs, prompt corrective action must be taken. Oftentimes, this action requires the placement of an ETT in the patient's trachea in order to restore or maintain an adequate airway. The process of inserting the tube in the patient is commonly referred to as intubation.
Over the years, various types of intubation devices have been developed for inserting endotracheal tubes in a patient. Perhaps the most commonly used intubation technique is a process known as direct laryngoscopy. In this technique, a device called a laryngoscope is used to actually visualize the upper airway through the patient's mouth during the process of inserting the ETT. This technique is usually successful in ensuring correct placement of the tube in the trachea in most patients. However, direct laryngoscopy is not feasible under all circumstances. Indeed, performing intubation on a relaxed, well-prepared patient in a hospital setting is much different than attempting to intubate an accident victim in a moving ambulance, helicopter or at the scene. Moreover, direct laryngoscopy has the disadvantage of increasing the risk of hypertension, tachycardia and dental and soft tissue trauma.
When intubation is properly performed, regardless of the procedure employed, the inserted end of the endotracheal tube will be positioned in the patient's trachea at a location substantially between the patient's vocal cords and carina. This location has been found to provide the best and most reliable airway management for several reasons. If the tube is not inserted far enough past the vocal cords, for example, it can become dislodged and ineffective, such as when it ends up in the esophagus. If the tube is inserted too far into the trachea, however, past the carina, then the tube may only function to adequately ventilate one of the lungs, rather than both. This can lead to serious complications. Thus, proper placement of the inserted end of the tube plays a major role in the intubation process.
Various techniques have been used in the past to attempt to ensure that the ETT lies in the proper location between the patient's vocal cords and carina after intubation. One such technique involves placing a light at the inserted end of the ETT prior to intubation. The technique is based on the principle of transillumination, i.e., that a strong light can be transmitted through the cartilage and soft tissues of the neck. It was further discovered that when the light at the end of the tube was clearly visible through the patient's skin in the area of the sternal notch, then the inserted end of the tube was approximately half-way between the vocal cords and carina in most patients. The absence of a clear glow of illumination in this area usually indicates incorrect placement, such as in the esophagus.
Even the most skilled and experienced laryngoscopist may encounter what is termed a "difficult" airway, which may occur in as many as 5% of all intubations. Difficult airways are identified several ways. A patient may report an extremely sore throat or nose after a previous surgery or there may be documentation on a previous anesthetic record. The jaw, teeth, mouth opening and neck motion are always examined prior to intubation to help gauge the difficulty of laryngoscopy. These maneuvers can identify many, but not all, difficult airways. In the traumatized patient, concern over a potentially unstable cervical spine that if manipulated, as is customary during laryngoscopy, could lead to paralysis is also considered a difficult airway. Of course, there is always the difficult airway that is discovered at the time of intubation despite no physical examination findings or surgical history to suggest its presence (unusual anatomy, undetected masses in the airway, etc.).
How the difficult airway is approached depends very much on the skill of the caregiver and the circumstances necessitating an ETT for the patient. Currently, a number of techniques are commonly employed. These include traditional laryngoscopy with or without axial cervical traction, fiber-optic bronchoscopy with or without a transtracheal retrograde wire guide, blind nasal and the lighted stylet techniques. Certain situations may preclude use of any of these methods and require emergent cricothyrotomy or tracheostomy.
The fiber-optic bronchoscopic technique is considered to be the method of choice in elective situations because it allows visualization of the vocal chords and trachea to confirm correct ETT placement. The major drawbacks with the fiberscope are (1) that it requires substantial expertise and (2) its poor performance in patients with copious secretions or blood in their airway. Thus, the patient is usually administered an anti-sialogogue to decrease secretions and a topical vasoconstrictor to reduce bleeding caused from the trauma that can be associated with oral and nasal intubations. Because blood so easily compromises the fiberscopic view and renders the fiberscope useless, it is often impractical and unnecessarily time-consuming to attempt this method of intubation in the traumatized victim. Although advances have been made in miniaturization of the fiberscope, the smaller-diameter fiberscopes that will pass through the smallest diameter ETTs are prohibitively expensive. Further drawbacks to the fiberscope are that it requires an external power supply for its light source, it is a large instrument and occupies substantial space at the patient's head, as well as for storage. All fiberscopes are expensive and sensitive instruments which are easily broken.
In selected patients, it may be preferable to employ the retrograde wire technique. This method requires that a needle be placed through the anterior neck into the trachea. A wire is passed through the needle and is then advanced upward through the vocal cords and pharynx until it emerges from the nose or mouth. The wire acts as a guide for either an ETT alone or a fiberscope loaded with an ETT. This method identifies the most prominent anatomical structure in the neck, namely, the trachea, and establishes a path for the ETT or fiberscope to follow in order to properly place the ETT there. One drawback to this technique is that it is invasive and risks introducing bleeding and infection into the trachea. Another drawback is that the wire must be stiff enough to act as a guide for the ETT alone. A stiff wire is more prone to injure tissues such as the trachea and vocal cords when advanced cephalad than would a more flexible wire. If the wire can act only as a visual guide for the fiberscope, then this method is also disadvantaged in bloody or secretion-abundant environments.
The lighted stylet is a device that incorporates aspects of both the fiberscope and retrograde wire techniques. In design, it is simply a stylet with a bright light at the distal end and a battery power source at the other end. An ETT is loaded over the stylet such that the light just emerges from the distal end of the ETT. When properly placed in the mouth, the light from the stylet will shine between the vocal cords into the trachea and the operator will see a pre-tracheal glow on the external neck. Once this glow is identified, the ETT is advanced and proper ETT placement reconfirmed through customary means [Birmingham et al, Anesth. Analg., Vol. 65, pp. 886-891 (1986)]. Thus, the lighted stylet is like the fiberscope in that it uses a light source in the airway and that the stylet acts as a platform from which to place the ETT. It is like the retrograde wire in that an observation or event occurs on the neck, namely, the pre-tracheal glow, that confirms correct positioning of the stylet. The lighted stylet overcomes many of the disadvantages of the fiberscope and retrograde wire techniques. Unlike the fiberscope, the lighted stylet is small, easily stored, rugged, does not require an extra power source, is disposable, relatively inexpensive and works well in a bloody environment. Unlike the retrograde wire technique, it does not risk additional infection or bleeding, and acts as its own ETT placement platform.
The lighted stylet method, however, is fraught with difficulties. Because it relies on the operator to appreciate a pre-tracheal glow before advancing the ETT, it is best used in a dark environment on thin and lightly pigmented patients. In fact, the lighted stylet is extremely difficult to use even by experienced operators in controlled situations if the patient has a large neck, is darkly pigmented or there is much ambient light. Unfortunately, visualization of the pre-tracheal glow may require the medical attendant to leave his customary position at the head of the patient and stand beside the patient. Intubation from this position is not necessarily more difficult, but it does significantly compromise the caregiver's ability to divert vomitus away from the airway if the patient regurgitates, and/or to stabilize the head and neck should the patient begin to move.
Furthermore, because of the light bulb that is at the tip of the stylet, its greatest outer diameter can only be reduced a small amount. Therefore, the lighted stylet will not easily pass through smaller-diameter ETTs. Children under the age of approximately 6 years would be too small to benefit from a lighted stylet. These pitfalls are commonly encountered by emergency rescue teams in the field, as well as in the emergency and operating rooms. Thus, the lighted stylet fails to achieve desirable design objectives of being a reliable intubation adjunct for all difficult airways because it can be used with confidence only with selected patients in selected situations.
A new method for securing the airway is needed. This method should be reliable under all conditions where emergent airway or difficult airways may be encountered. It must work equally well in bright light and in the dark. It must be lightweight, small, portable, durable and inexpensive. It must be able to function properly in all sizes of patients, in patients with light or heavy pigmentation and in situations where there is blood in the airway. Finally, it must not require an excessive amount of experience to use the device with effectiveness and safety.
It is an object of the present invention to provide an intubation system and method which satisfies these criteria and overcomes the disadvantages associated with the prior art devices.